A device for an adjustment mechanism of a vehicle seat is already known from DE 32 03 151 A1, which comprises a drive element which can be driven in opposite directions of rotation and a driven element which can be driven by means of this drive element and can be pivoted in opposite directions of rotation. In the device proposed therein, two unilaterally acting freewheels are provided between the drive element and the driven element, said freewheels being connected to run in opposite directions so that the locked direction of the first of these freewheels corresponds to the free running direction of the second of these freewheels and the locked direction of the second of these freewheels corresponds to the free running direction of the first of these freewheels. The freewheels are assigned a common (inner) toothing (notched formation) arranged along a circular path.
Each of the unilaterally acting freewheels has a (separate) catch or pawl, which is pivotably held on a respective bearing bolt fixed to the drive element and is pressed in a spring-loaded manner against the toothing. The spring provided for this purpose is configured as a helical spring acting as a tension spring, which engages with its distal ends at one side in the pawl of the first freewheel and at the other side in the pawl of the second freewheel.
For the relative rotation of the driven element with respect to the drive element, in the configuration known from DE 32 03 151 A1 an unlocking device is provided for optionally bringing in each case one of the freewheels out of engagement. This unlocking device is formed by means of an essentially hollow semicylindrical collar which extends on a rotatably mounted handwheel which serves as the driving actuating device for the drive element. In the event of an external torque acting on the handwheel about the axis of rotation thereof, then depending on the orientation of the torque said collar in each case loads one of the pawls in such a way that it, or the freewheel of which it forms part, comes out of engagement and, if the torque on the handwheel continues without any change in orientation, strikes a pin fixed to the drive element which is different from the aforementioned pin, so that the handwheel subjected to a torque from outside drives the drive element in rotation via the engagement of its collar in the respective pawl and the coupling thereof to the stop pin fixed to the drive element. The drive element in turn entrains the driven element in rotation via the other unilaterally acting freewheel which is still in engagement, on which driven element the toothing of the two freewheels is formed.
In order to pivot the driven element in the opposite orientation, the handwheel can likewise be subjected to a torque in the opposite orientation. Starting from the position run through in this case, in which the two freewheels are still in engagement, the relationships mentioned above are reversed, so that the freewheel which was brought out of engagement above instead remains in engagement and is used to transmit torque to the driven element, and accordingly the other freewheel is brought out of engagement by means of the collar.
It should be noted that a stop pin of the aforementioned type is also provided for the freewheel which is then not in engagement, so as to allow the transmission of torque from the handwheel to the drive element in this other direction of rotation.
This device known from DE 32 03 151 A1 appears in principle to be highly suitable for adjustment mechanisms of vehicle seats. However, one disadvantage with this configuration is that the fineness with which the vehicle seat can be adjusted largely depends on the motor capabilities of the user.